Modern aircraft, in particular commercial aircraft, incorporate a plurality of fluid systems, i.e. systems in which a fluid is guided through corresponding lines during operation. The systems, which are generally described as “fluid systems” here, include for example the air conditioning system, the water supply network and the diverse hydraulic systems of the aircraft. In the case of many of these systems, a plurality of consumers are supplied with a fluid, i.e. a liquid, a gas or a liquid/gas mixture, by a single fluid source, with the term “consumers” here not only referring to “end consumers”, i.e. components and systems on board the aircraft which are to be supplied with fluid during operation, but also “continuing” lines, i.e. lines of the fluid systems which are arranged downstream of a line bifurcation and are supplied with fluid by a common supply line arranged upstream of the line bifurcation.
During operation of the fluid systems, operating situations can arise in which it is desirable or necessary to influence a fluid distribution to a plurality of consumers in such a way that the supply of fluid to one or more selected consumers is granted greater priority than the supply of fluid to another consumer or other consumers. For example, consumers which fulfil safety-relevant functions on board the aircraft have greater priority in the supply of fluid than consumers whereof a failure merely affects comfort on board the aircraft. Prioritising individual consumers in the supply of fluid is particularly expedient if the fluid pressure or fluid volume flow provided by a fluid source is not sufficient to supply fluid adequately to all the consumers to be supplied with fluid by the fluid source.
Priority valve assemblies 100, 100′ shown by way of example in FIGS. 1 and 2 are therefore used in different fluid systems on board an aircraft. In the priority valve assembly 100 shown in FIG. 1, a priority valve 102 is connected on the inlet side to a fluid supply line 104 and on the outlet side to two fluid discharge lines 106, 108 which are to be supplied with fluid parallel to one another by way of the fluid supply line 104.
If an inlet fluid pressure pE which is sufficient to supply a desired fluid volume flow to both fluid discharge lines 106, 108 acts on the inlet side of the priority valve 102 by way of a control pressure line 110, the priority valve 102 is located in a position which ensures that a desired fluid flow, which may optionally also be varied depending on the operating situation, is supplied to both fluid discharge lines 106, 108. On the other hand, if the inlet fluid pressure pE acting on the inlet side of the priority valve 102 falls below a predetermined threshold value for which an adequate fluid supply to both fluid discharge lines 106, 108 can no longer be ensured, the supply of fluid to the first fluid discharge line 106 is prioritised over the supply of fluid to the second fluid discharge line 108, i.e. the priority valve 102 moves into a position in which the priority valve 102 maintains the fluid supply from the fluid supply line 104 into the first fluid discharge line 106, but throttles or, if necessary, also completely interrupts the fluid supply into the second fluid discharge line 108.
In the priority valve assembly 100′ shown in FIG. 2, a priority valve 102′ is connected on the inlet side to a fluid supply line 104′ from which a first fluid discharge line 106′ branches off upstream of the priority valve 102′. On the outlet side, the priority valve 102′ is connected to a second fluid discharge line 108′ which is to be supplied with fluid by way of the fluid supply line 104′.
If, by way of a control pressure line, the inlet side of the priority valve 102′ is acted upon by an inlet fluid pressure pE sufficient to supply a desired fluid volume flow, which may optionally also be varied depending on the operating situation, to both fluid discharge lines 106′, 108′, the priority valve 102′ is located in an open position so that the desired fluid volume flow is supplied to both fluid discharge lines 106′, 108′. On the other hand, if the inlet fluid pressure pE acting on the inlet side of the priority valve 102′ falls below a predetermined threshold value for which an adequate fluid supply to both fluid discharge lines 106′, 108′ can no longer be ensured, the supply of fluid to the first fluid discharge line 106′ is prioritised over the supply of fluid to the second fluid discharge line 108′, i.e. the priority valve 102′ moves into a position in which the priority valve 102′ throttles or, if necessary, also completely interrupts the fluid supply from the fluid supply line 104′ into the second fluid discharge line 108′ so that the fluid supply from the fluid supply line 104′ into the first fluid discharge line 106′ branching off from the fluid supply line 104′ upstream of the priority valve 102′ can be held at a desired level.